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Date: Wed, 25 Aug 2021 10:49:04 +0800
From: butt3rflyh4ck <>
Subject: Linux kernel: fs/btrfs: null-ptr-dereference bug in
 btrfs_rm_device in fs/btrfs/volumes.c

Hello, there is a null pointer dereference bug in the btrfs_rm_device
function in fs/btrfs/volumes.c in linux-5.14.0-rc4+ and reproduce too.
Fortunately, triggering the bug requires ‘CAP_SYS_ADMIN’.

#Root Cause
When a user invokes a BTRFS_IOC_RM_DEV_V2 ioctl to remove a non-exist
volume device,
it would call btrfs_ioctl_rm_dev_v2 function to implement. And
btrfs_ioctl_rm_dev_v2 would call btrfs_rm_device,
if the id of the volume device is illegal, it would trigger a
null-ptr-deref bug to cause DoS.

# Analyse

the patch for this issue, not available upstream now.

*2021/8/6 - Vulnerability reported to maintainer and CC to
*2021/8/6 - Vulnerability confirmed and patched.
*2021/8/10 - Vulnerability reported to
*2021/8/25 - Opened on

the issue is reported by Active Defense Lab of Venustech.

Active Defense Lab of Venustech

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